Radio receiver with band-spread tunable circuits



Jan. 24, 1950 BLQK ET AL 2,495,624

-SPREAD TUNABLE CIRCUITS RADIO RECEIVER WITH BAND Filed Feb. 8, 1947 K PR 0L T s R W N Nmm w v m 4% 5 Y M B R N E H AGENT like are manifest in an annoying manner.

Patented Jan. 24, 1950 UNITED RADIO RECEIVER WITH BAND-SPREAD TUNABLE CIRCUITS Henri Rick and Henric Netherlands,

hoven, National Conn., as

Bank and trustee us Adrianus Broos, Eindassignors to Trust Company,

Hartford Hartford,

Application February 8, 1947, Serial No. 727,346 In the Netherlands March 16, 1944 Section 1, Public L Patent expir This invention relates to a radio-receiver, of which one or more resonant circuits can be wave ranges.

In the common receivers of this kind several comparatively narrow wave bands in the range of the short waves, which may be deemed to be of particular importance e. g. the broadcast bands or the amateur bands and which will be called short wave bands hereinafter, are spread out through-out the width of the dial scale. In order that the same tuning condenser may be used as in tuning in the long and medium wave range, one or more fixed condensers are connected in series and/or in parallel with the variable eondenser in band-spread tuning.

The short wave bands to be spread having a width of 300 kilocycles/sec. at the most, the slope of the tuning curve indicating the tuning frequency as a function of the point of the hand with respect to the scale, is much smaller than the slope on tuning in the medium wave range.- This has the drawback'that small shortcomings of the receiver, such as frequency variations of the local oscillator, play of the tuning means or the over, the wave length switch must have an tional position for reception of the whole of the short wave range to permit of tuning also to ranges in between the short-wave bands.

The invention has for its object to ensure a suitable tuning to short waves by simple means, in which one or more short wave bands are spread to a suincient degree and the ranges beyond these ing at least to the distance between two neighbouring short wave bands, is covered, at least one i short-wave band being spread.

The invention is based on the recognition that by the said series and/r parallel connection not only the range of variation of the tuning reactance and consequently the average slope of the aw 690, August 8, 1946 es March 16, 1964 7 Claims. (01. 25040) tuning curve is reduced, but also the slope of the tuning curve at one or more points is so slight as to permit a short-wave band to be spread at these points.

.sion or alternately.

points beyond the short wave bands.

In order that .the invention may be clearly understood and readily carried into effect, it will now be explained accompanying drawing, representing, by way of example, several embodiments thereof.

Figure 1 represents a preferred embodiment of the invention;

Fig. 2 illustrates graphically the operation of the circuit shown in Fig. 1;

Fig. 3 and 4 show alternative arrangements of a receiver dial scale as referring to the band spreads graphically represented in Fig. 2;

ing use of a copper core.

-ance of coil 4 and "the slope of the range being covered from 13'to "mainly brought the variation *thermoreFig.

were kept constan.

" in'the range T in Fig. 5 represents a further graphical illustration of the circuit shown in Fig. 1;

Fig. 6 showsa receiver dial scale for cal representation shown in Fig. 5;

Fig. 7 shows a further embodiment of the invention; and

Fig. 8 shows graphically the operation of the circuit shown in Fig. 7.

Fig. 1 represents a resonant circuit which constitutes, for instance, the oscillator circuit of'a radio receiver according to the invention and is shown in the circuit arrangement used in tuning in a short wave range. The resonant circuit includes a variable condenser iwith which a fixed condenser 2 is connected in parallel; with this parallel-connection is provided a fixed condenser 3 and an inductance coil t whose inductance can be varied by means of a movable core 5 of ferromagnetic or conducting material. In practice good results are obtained when mak- The inductanceva'riation to be obtained byshiiting the core*may,..for instance, amount to "from 201to 30% of the maximum value. The tuning condenser 1i and=the the graphi- -core "5 are mechanically 'intercoupled 'and are 1 controlled by a common tuning device. placement rived from mean's of a variable coupling, e.: 'g.-a cam disc.

.Theidis- 'ofthe core may, forinstance, be dethe shaft of the-tuning condenser by -However, the desired variation of theinductance "catn a'lso beobtained-when making .useo'f a composite core which consists partly of ironand-part- -1yof' copper and 'whos displacement is derived through-a direct coupling from the shaft-of-the tuning condenser. nantcircuit the tuning condenser I is usedatthe same time for tuning the receiver-in-the 'long and medium wave range.

Fig. 2- illustrates the-product LC of the inductthe capacity connected. in .par- :allel with the coil as -a' functionbf the position a of the-dial pointer with respect to the dialscale, the points of two short wave'bands to be spread being designated by I and II along the ordinate axis.

By a suitable size of the condensers Zand3 and a suitable variation of the inductance of coil "4 it can be ensured that theproductLC variesas a function of theposition of'the dial pointer according to curve a, the short wave band'I'bein'g "spread out overthe dial scale 'part 'designate'd'by B and the short wave band II over the dial-scale part D. In between these partsthere' is arange "T,"in which no spreadingtakesplacearrdin which may substantially tuning curve that in the case of the short wave 50 m. without without making use of band- 2 -and -3' and the variacorrespond with changing over and spread. The condensers tion of the inductance are preferably so chosen that the spread of the short-wave band II is about by the condenser 3, and the short wave i band I 'mainly'by of the inductance of coil 4. :Fur- '2 shows (see curve b) how theproduct' LC would vary it the inductanceof coil 4 Thereby the spreading of the short wave band 11 having the greatest wave the spread of length is not or substantially not afiected,"but

the short wave band I having the smallest wave length is spread out over .a materially smaller range B, whereas the slopezof the-tuning curve between the :bands has'slightly decreased.

In principle it is 'also'feasible,

and inseries After changing overthe reso- --parts of the short .-:Erin Fig... 2-) ,and'the more fiat tuning may'notbe possible in the range .tained by making traversing thearea direction-of range .13,-

=inductance oi..coi1 4 is .caused .to decrease -and in the area v'Itis brought about an increase,

anlincrease oi the inductance.

waves to be Scan be provided on the scales -or short "wave ranges, in.) and II "(16 "short wave bands III "(20 mi) and -Z. If desired, the short wave whereas in the *withoutbandspread. This arrangement isshown irfFigc-4, wherein same ban'ds as =.in F.i'g. 3, VI -m. bandandv'l" .-..ing'dial scale parts is the .same as when .the shortwave rangeiof from 13'to 50.m. were covered without :changing -over; -of banriespread. If .desired-all-bandson the dial scale may be given-the same width by .usingaa 4 choice of the condensers 2 and 3, to secure a sufflcient spreading of the two short wave bands without variation of the inductance of .coil 4. The use of the inductance variation has the advantage, that the slope of the tuning curve in the various wave range can be adjusted entirely at will. Moreover, the inductance variation-may be utilised to ensure a suitable closing up of the short wave ranges, among which the short waves to be received are distributed.

'In the .aforesaidicircuit arrangement, in efiect, 'theproduct'LC is very flat at the beginning and the end of each short wave range (ranges A and as the spreading bands is better. As a result, between two short wavebands which occur in different short wave ranges, because the various short wave ranges do not adjoin each other.

This evil can be cured by varying in "the short wave the inductance of coil kin the range A and/or. in the range .in :a suitable manner, e. .g. .in .such .a manner that-the product LC variesraccording to the curve which vcoincides-with-the curve a in the .ranges B, .I and D -but exhibitsa much steeper slopein the areas A and E. Such a variation canbeob- .the inductance of coil '4, on .A,,gradual1y increasein the e. ,gby. moving .aniron .core entirely or partly .into theboil. .After that the again,

the areal?! again 'As the caseimay bethe inductance in the area'D maybe kept'constant. The short wave range, which is'c'overed when no inductance variation is used in the ranges A and'E is represented *by'PQ in Fig. '2. When using the said inductancevariation'this range 'is widenedtoP'Q'fasawesult of which the shortwave ranges5among which-the short received are distributed, "adj oin or even overlap each other.

.Fig. "3 "illustrates how the short wave bands the various the short 'wave ban'ds' I (1 3 scale); the IV (25 'm.) figuring on'scale "Y'and the short wave bands V '(30 m.) and VI (4i) to -50 'm-.-) appearingbn scale bands :may :also be-arrange'd in such a manner as 'to spread'the 40 m. band 'and'the'50 m. band'each individually, I3 "m. band tuning takes 'place .inthe-area D adecrease and in m.) appearing on the figures II to N .-:denote the tdesignating the-=40 "denotingtthe :m.-.band. In

"a particularly suitablecexecutionalexample the widths of the ion-the 'dial scale are so rchoseni-that:B==D==A+T+E. .If-this condition be satisfied, the aslope :of the tuning curve in thefshortwave to oris slightly smaller than that bands'substantially corresponds in the. medium wavefrange, whereas-the slope 'Ior theremainand without making use .short wave range,.so that I separate coil for each the inductance variation as La .iunction .of the ,position .of the -.-dial .pointer .with. respect .to the .scale canby "a suitable as wave range.

beadiusted: separatelyior each short Fig. represents the tuning curve of another embodiment of the invention, in which the first short wave band I is at the beginning of the dial scale (range B), and the second short wave scale (range D). the first short wave band is mainiy obtained by short-wave band mainly by means of the series-condenser 3. If in this case in such a manner that an increase in capacity of the condenser l involves an increase in inductance of coil 4. In

VI and VI" can then be obtained by causing the inductance, in the short-Wave range corresponding with dial scale Z, to increase less Instead of the variation of the inductance of coil 4, the desired variation of the tuning curve may also be obtained by means of a special conobtained when switching oif the correcting condenser 6, and the curve c representing the capacity variation of the condenser 6. The maximum capacity of the correcting condenser may tain circumstances the parts of the circuit may be given such a size that the short-wave band at the end of the dial scale is spread to a sufficient degree without variation of the correcting condenser. In this case the capacity of the correcting condenser 6 may also vary according to curve I. When equipping the correcting condenser with two or more stators, each of which act in a diiierent short-wave range, the desired capacity variation can be obtained in each shortwave range.

What we claim is:

1. A resonant circuit arrangement to provide band-spreading for radio receivers comprising,

nect said third capacitative element in parallel with a portion of the series connection of said from said given rate relative to each other over a second portion of the tuning range of said e1ements.

2. A resonant circuit arrangement to provide band spreading for radio receivers comprising,

second portion of the tuning range of said elements.

range of said elements.

4. A resonant circuit arrangement to provide band-spreading for radio receivers comprising, a

range of said elements.

5. A resonant circuit arrangement to provide band-spreading for radio receivers comprising, a variable capacitive element, a fixed capacitive element in parallel with said variable capacitive element, a variable inductive element connected in parallel with the said variable capacitive element and the said fixed capacitive. element, and means to mechanically couple said variable capacitative element and said variable inductive element and to vary the value of said variable elements at a given rate relative to each other over a first portion of the tuning range of said elements and at a rate difierent from said given rate relative to each other over a second portion of the tuning range of said elements.

6. A resonant circuit arrangement to provide band-spreading for radio receivers comprising, a variable capacitive element, a fixed capacitive element connected in series with said variable capacitive element, a variable inductive element connected in parallel with the said series-connection of the variable capacitive element and the fixed capacitive element, and means to mechanically couple said variable capacitative element and said variable inductive element and to-vary the value of said variable elements at a given rate relative to. each other over a first portion oiv the tuning. range of said elements and at a rate different from said given rate relative to each other over a second portion. of the tuning range of saidelernents.

7. Av resonant circuit arrangement to provide band-spreading for radio receivers comprising, a first variable capacitive-element, a fixed capacim tive element in series with said variable capacitive element, a second variable capacitive element connected in parallel with said series connection of the first variable and fixed capacitive element, an inductive element connected in par- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,095,035 Posthumus et a1. Oct. 5, 1937 2,129,026 Van Roberts Sept. 6, 1938 2,288,236 reen 1 June 30, 1942 2,312,211 De Cola Feb. 23, 1943 FOREIGN PATENTS Number Country Date 38,349 Holland May 16,1936 551,064 Great Britain Feb. 5, 1943 552,403 Great Britain Apr. 6, 1943 OTHER REFERENCES Wireless World for -131. Copy in Div. 10.

Wireless World for November 1'7, 1938, pages 443-44. Copy in Div. 10.

February 1940, pages 

